Revelation 4:3

He that sat. Here again only the participle is (see on v. 2).

Jasper. Gr. iaspis, not precisely the modern jasper, but a stone described by the ancient naturalist, Pliny, as translucent (Natural History xxxvii). John has recourse repeatedly to precious stones for describing brilliant colors, for sunlight shining on such stones produced some of the most brilliant colors known to man in his day. In the present instance, the iaspis probably describes a bright, flashing light, more notable for its brilliance than its color.

Sardine stone. The carnelian or some other stone of a reddish color. Pliny (ibid.) notes that this stone was to be found at Sardis, and accordingly took the name of that city. Here it describes a brilliant red light.

Rainbow. Compare Ezekiel’s vision of the throne of God (Eze. 1:26–28).

Like unto an emerald. That is, of a green color. The brilliance of the light flashing forth from the presence on the throne is tempered by the soft green light of an encircling rainbow. This rainbow represents the combination of justice and mercy that characterizes God.